docs: def process_runway_configs(runway_dir=''):
      """Read the _application.json_ files.
  
      Args:
          runway_dir (str): Name of runway directory with app.json files.
  
      Returns:
          collections.defaultdict: Configurations stored for each environment
          found.
      """
      LOG.info('Processing application.json files from local directory "%s".', runway_dir)
      file_lookup = FileLookup(runway_dir=runway_dir)
      app_configs = process_configs(file_lookup, 'application-master-{env}.json', 'pipeline.json')
      return app_configs